Prostaglandins (PGs) are part of the prostanoid family and their receptors fall into five different classes—DP, EP, FP, IP and TP—based on their sensitivity to the five naturally occurring prostanoids, PGD2, PGE2, PGF2α, PGI2 and TxA2, respectively (Coleman, R. A., Prostanoid Receptors, IUPHAR compendium of receptor characterization and classification, 2nd edition, 338-353, ISBN 0-9533510-3-3, 2000). EP receptors (for which the endogenous ligand is PGE2) have been subdivided into four types termed EP1, EP2, EP3 and EP4.
The international patent applications WO2005080367 and WO 2007017687 describe various EP2 receptor agonists and the use thereof for the treatment of conditions like inflammatory disorders, asthma and chronic obstructive pulmonary disease.